XF 1.5 Cannot select partial text like its gone in the background

If you scroll down to my site to the statistics you can partially select the text there hovering over the users. At the right side there seems to be a invisible block or something blocking the text. I have no idea what causes this.
It is an add-on- the user statistics but i feel there is a simple matter of some wrong css code what causes this.http://cupcakethunder.eu/index.php?forums/